Given a story and/or a picture, a computational model can be created by first identifying the data structure of the model. The data structure describes which data the model needs to keep track of in order to accurately represent the phenomenon being modeled.

This problem challenges you to take an existing story and picture and create a data structure that could be used in a computational model representing the behavior described.

The model we are working with is described in a previous challenge problem ("Picture This: Precipitate", http://hpcuniversity.org/students/weeklyChallenge/70/).

A picture depicting the model is attached below as "Picture This: Precipitate Image".

A solution will consist of a data structure, written clearly in English or pseudocode, indicating what data will be need to be kept track of while computing the model. This data structure should be written in such a way that it could be used in the future as part of an algorithm.